A Wireless Local Area Network (WLAN) is a Local Area Network (LAN) that employs wireless communication such as radio frequency (RF) or infrared (IR) transmission. A WLAN typically comprises fixed-location transceivers known as access points (APs) to which client devices connect via RF technology. The access points typically are hard wired to switches and routers that interconnect them and provide access to servers. The APs are fitted with radio transceivers and omnidirectional antennas. The client transceivers, or network adapters, may be in the form of Personal Computer Memory Card International Association (PCMCIA) cards, for example. The APs are located at central points where there is good line of sight (LOS) to the client devices and link quality, therefore, is best. Most WLANs are standards-based versions from the IEEE 802.11 Working Group. (For any IEEE standards recited herein, see: http://standards.ieee.org/getieee802/index.html or contact the IEEE at IEEE, 445 Hoes Lane, PO Box 1331, Piscataway, N.J. 08855-1331, USA.)
A wireless mesh network is a collection of wireless nodes or devices organized in a decentralized manner to provide range extension by allowing nodes to be reached across multiple hops. In a multi-hop network, communication packets sent by a source node can be relayed through one or more intermediary nodes before reaching a destination node. A large network can be realized using intelligent access points (IAP) which provide wireless nodes with access to a wired backhaul. A mesh network therefore typically comprises one or more IAPs (Intelligent Access Points), and a number of APs (Access Points), which provide data service to STAs (subscriber stations). An AP can connect to IAP directly or through multi-hop route.
A key aspect for optimal performance of a WLAN mesh network is controlling and coordinating the transmissions from different devices to minimize interference and collisions among the devices of the mesh network. To do so, in one method incorporating Scheduled Mesh Access (SMA), nodes transmitting data at known intervals advertise the timing of future transmissions to all nearby nodes that implement scheduled mesh access (SMA). The SMA mechanism reserves time on a media for future transmissions, and then accesses the media at reserved times using 802.11 channel access procedures. Further details of scheduled mess access operation, for example, can be found in United States Patent Publication Number 20090052463 entitled “Method Of Communicating Within A Mesh Network,” filed on Aug. 24, 2007, assigned to the assignee of the present invention, and herein incorporated by reference in its entirety.
Advertisements may be broadcast to indicate when the channel will be busy. This can prevent nearby nodes implementing scheduled mesh access from accessing the channel at reserved times, thereby reducing collisions on the wireless LAN channel. Advertisements, such as messages advertising when a node is going to be sending or receiving traffic or advertising when a node expects its neighbors to send or receive traffic, are typically broadcast to mesh neighbors in management frames, a technique which works well when the omni-directional range of a node is large enough to reach all the neighbors of a node. However, if some nodes employ advanced antenna techniques, such as beamforming, to improve link rates or extend range, the advertisements broadcast to all neighbors via omni-directional antennas may not reach all of the neighbors that could be impacted by the beamforming-based data transmission.
Accordingly, there is a need for antenna-aware method to transmit packets in a WLAN mesh network.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.